Health experts exclusively talking to The Tribune say the familiar description of dengue as a “monsoon disease” no longer reflects the reality on the ground, even as the country continues to navigate the long and complex road towards an indigenous vaccine.
“Yes, this label isn’t just outdated; it’s actually dangerous. When people treat dengue as purely a monsoon problem, they let their guard down for the other eight months. And that’s exactly the gap dengue is exploiting now,” said Dr Shikha Taneja Malik, senior scientific affairs manager, Drugs for Neglected Diseases initiative, South Asia.
She said dengue transmission was no longer restricted to the traditional July to November window. “We’re seeing cases even in safe months like February, March, and May. Cities like Delhi, Mumbai, and Bengaluru, which used to have a clear off-season, are now reporting transmission almost year-round.”
According to Malik, the increase in transmission is being driven by rising temperatures, changing rainfall patterns, unplanned urbanisation and poor sanitation. While monsoon months are still expected to witness the highest burden, she said the disease is increasingly becoming a year-round public health challenge.
The changing disease pattern comes at a time when India is pushing ahead with dengue vaccine development, a process experts say is far more demanding than it appears.
“Developing a safe and effective dengue vaccine is scientifically far more complex than for many other viral diseases,” said Dr Manisha Arora, director, Internal Medicine at CK Birla Hospital, Delhi.
She explained that dengue had four distinct serotypes and immunity against one did not ensure protection against the others. A phenomenon known as antibody-dependent enhancement can also increase the risk of severe disease following infection with another serotype if immunity is not balanced well. The experience with the first licensed dengue vaccine has led regulators worldwide to demand stronger evidence on safety and long-term protection before approving newer vaccines.
Malik said India possessed strong scientific capability but faced a major hurdle in translating research into successful vaccines. “India has a strong foundation in basic academic research. However, the ‘valley of death’ — the transition from a lab bench candidate to Phase I/II clinical trials — is quite huge.”
She said large efficacy trials involving tens of thousands of participants required significant investment, regulatory oversight and operational capacity. Among the indigenous candidates, Panacea Biotec’s DengiAll vaccine, developed with ICMR, has recently completed recruitment for its Phase III clinical trial involving more than 10,335 participants across 19 sites in 18 states. Participants will now be followed for two years.
Malik also noted that the recent approval of Qdenga in India by the DCGI, with manufacturing planned by Biological E, reflects improving regulatory preparedness. However, she said existing vaccines were recommended only for specific age groups, leaving populations such as pregnant women, newborns and older adults without protection.
Experts also sought to correct another common misconception surrounding the disease.
“It is important to clarify that dengue is not classified by the World Health Organization as a rare disease. Rather, it is recognised as a Neglected Tropical Disease,” Arora said.
She said the classification reflects the fact that dengue disproportionately affected tropical and subtropical regions where poverty, inadequate sanitation, rapid urbanisation and weak mosquito control continued to drive transmission. Despite causing hundreds of millions of infections globally each year, the disease has historically received comparatively lower investment in research and development than many other infectious diseases.
Both experts stressed that vaccines alone will not be enough to curb the growing burden of dengue.
“Until highly effective preventive tools become widely available, early testing and source reduction remain the most effective strategies for reducing dengue-related illness and deaths,” Arora said.
Calling for sustained investment in research, surveillance and treatment, Malik said, “India has the scientific knowledge and manufacturing capability; all that is now required is the commitment to pursue it.”
As dengue spreads beyond its traditional season, experts say the country’s response must also move beyond seasonal campaigns, combining stronger surveillance, sustained mosquito control, timely diagnosis and continued investment in vaccines and new treatments.
The Tribune, now published from Chandigarh, started publication on February 2, 1881, in Lahore (now in Pakistan). It was started by Sardar Dyal Singh Majithia, a public-spirited philanthropist, and is run by a trust comprising five eminent persons as trustees.
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Remembering Sardar Dyal Singh Majithia
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